Nick has 4 more 20-cent coins than 10-cent coins. After he used 16 of his 20-cent coins, the total value of 20-cent coins is $4.20 more than the total value of 10-cent coins. How many coins did he have at first?
| |
20¢ |
10¢ |
| Before |
1 u + 4 |
1 u |
| Change |
- 16 |
|
| After |
1 u - 12 |
1 u |
| |
20¢ |
10¢ |
| Number |
1 u - 12 |
1 u |
| Value |
20 |
10 |
| Total value |
20 u - 240 |
10 u |
$1 = 100¢
$4.20 = 420¢
Number of 20¢ coins in the end
= 1 u + 4 - 16
= 1 u - 12
Total value of 20¢ coins in the end
= 20 x (1 u - 12)
= 20 u - 240
Total value of 10¢ coins in the end
= 10 x 1 u
= 10 u
After using 16 20-cent coins, the value of 20-cent coins is 420¢ more than the value of 10-cent coins. If another 420¢ is added to the 10-cent coins, the total value of 20-cent coins and 10-cent coins will be the same.
20 u - 240 = 10 u + 420
20 u - 10 u = 420 + 240
10 u = 660
1 u = 660 ÷ 10 = 66
Number of coins that Nick had at first
= 1 u + 1 u + 4
= 2 u + 4
= (2 x 66) + 4
= 132 + 4
= 136
Answer(s): 136
